From small appliances like toys, credit card readers, keyboards, colour TVs, refrigerators, air-conditioners, microwave ovens to large machines such as cars, industrial auto systems, outdoor advertisement displays, robots and even military missiles, they are not operated by formal OS-based computers. Instead, single chip microcomputers or controllers are used.
Single chip microcontroller is an important branch of development of microcomputers which became popular since 70s of the last Century. It belonged to a kind of Large-Scale Integrated Circuit, consisting of CPU, RAM, ROM, I/O interface and Interrupt System embedded in a single silicon chip. After the 80s, single chip controllers experienced very rapid development, applications involving these chips were used in a lot of fields, automation facilities in particular. As a result, many advanced models of microcontrollers were available in the market. It soon appeared to be a key hardware installation requirement for pillar industries. Owing to high demands, retail prices of these chips are competitively low.
A functionable computer has the following main parts: CPU (computing, control), RAM (memory, storage of data), ROM (storage of programs), I/O interface (serial port, USB, parallel output）etc. They are planted as different chips and accessories, on a sophisticated motherboard. However, for a single chip microcomputer, all these are integrated in a single chip.
Advantages in using single chip controls include inexpensive, involve less sophisticated circuits, small size and low power consumption. They are extensively used in industrial applications. For example, controlling the motor of a washing machine to achieve special functions can be done without using a computer, a single chip controller coupled with a suitable driving circuit will do the job (Fig. 283).
Intel 8051 is the masterpiece of early single chip microcontroller |  |
| Intel P8051 |
8051 is an 8-bit single chip microcontroller, a kind of MCS-51 Large-Scale Integrated Circuit chips, manufactured by Intel in 1981. As of now, sustained development involving big manufactures like Intel, Texas Instruments, Microchip, Silicon Labs, Philips, Winbond etc produced advanced prototypes with strong compatibilities.
8051 consists of four parallel 8-bit ports, which are programmable as well as addressable as per the requirement. An on-chip crystal oscillator is integrated in the microcontroller having crystal frequency of 12 MHz. 8051 single chip microcontroller used synchronized serial logic system, entirely dependent on the internal clock signal, generating various periodic instructions and in phase signals. Intel’s original prototype used NMOS technology, but later versions used CMOS technology instead and renamed with a letter C (e.g. 80C51). C models consumes less power and are more suitable for portable devices using batteries.
Working principle and applications of 8051 had been included in all higher institute/
university as standard first year electronic engineering program for single chip microcontroller introductory study.
(Fig. 276) Scheme of internal structure of 8051
Basically, single chip microcontroller is a kind of hardware. It has to be coupled with suitable software for practical use. Like personal computers, early models mainly used Assembly Language for programming. Later, C Language was adopted for the ease of compilation and also for higher compatibility and speed.
A brief introduction to illustrate how a single chip microcontroller works.
Project: A blinking LED
Circuit for the project objective is shown in (Fig. 277), using AT89S51 (8051 family) as the controller. The chip was programmed using Assembly Language (Fig. 278). The purchased chip has no built-in programs and has to be programmed by a computer and checked for errors followed by corrections by an emulator or simulator (refer to Topic 10.2 for details).
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| (Fig. 277) Blinking LED circuit | (Fig. 278) Assembly Language program | (Fig. 279) Set up |
10.1 Bit number of single chip microcontroller
According to the width of the system bus (a bus is a communication system that transfers data between components inside a computer) or the processor register (a register is part of the CPU), single chip microcomputers are classified as 4 bit, 8 bit, 16 bit or 32 bit based. 4-bit single chip microcomputers are mostly used in refrigerators, washing machines and microwave oven domestic appliances (Fig. 283). 8-bit and 16-bit chips are mainly for automatic control purposes and they usually do not use OS. Network or multimedia systems use 32-bit chips for handling complex operations, normally based on Embedded Operating System.
The Intel single chip microcomputer series
* 8-bit The 8051 series:
The 8051series enjoyed historical development, resulting in high compatibility and widespread scope of applications.
8XC42
MCS48
8xC251
* 16-bit
MCS96 Series
MXS296
* 32-bit
i960
10.2 Development of single chip microcomputers
Like most software development stage, single chip microcomputer used Assembly Language as the starting programming language. Later on, more and more users used C Language or the beginner-oriented BASIC Language, some IDE (Integrated Development Environment) support C++.
Unlike traditional desktop computers, available OS based softwares are either built-in, e.g. MicroSoft Windows “Office” or on-line commercially available like “Adobe Readers”, “Flash Player” etc, software of single chip microcomputer has to be self- devised, as the output has to meet the requirement set by the designer. Also, once checked to be perfect, the self-designed software will be incorporated into the chip and go with the IDE board like a permanently sealed set, notably those designed for outdoor display visual boards
Chips like 8051 goes with peripheral components so that the whole package acts as a hardware development kit (Fig. 280). 8051 itself has to be programmed for instruction operations. Traditional way of doing is to unplug the chip from the development kit and feed it to an emulator or simulator (Fig. 281) solely for the purpose of program writing and checking. The emulator will be connected to a computer from which programs are written and downloaded to the emulator for checking. Once possible errors are corrected, it will be fixed by using programmer. The finished chip will be mounted onto the kit board again and get ready for on-site application followed by a pre-set scale of production. ROM-based microcontrollers are adopted for large volume production. Alternatively, EPROM (erasable programmable read-only memory) are used for prototyping and limited applications
This kind of practice of installation was found to be tedious and time consuming. After Millennium, MCU (microcomputing unit) experienced rapid development, a lot of single chip models adopted the built-in ISP (In-System Programming) design (Fig. 282), in which programming can be completed with the chip mounted onto the kit board and not necessary go through a simulating procedure. Another improved method was to use IAP (In-Application Programming) in which the MCU can fetch new program from the system and renew on its own. Both methods overwhelmingly changed the domination of traditional way of development by using emulator. This mode of production reduces cost and saves time, simplifies production process and promotes cost-effectiveness. Chips of this kind includes the AT89S series and the AVR series.
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(Fig. 280) A 8051 demonstration kit | (Fig. 281) An emulator for 8051 | (Fig. 282) AVR ISP development board |
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(Fig. 283) Applications of 8051 or its derivative | (Fig. 284) Commercial advertisement display board |
Street scene application of single chip controller
Currently, the most popular single chip microcontroller is the Arduino chip board and its IDE applications (Fig. 285, 286). Arduino chip used ICSP (In-Circuit Serial Programming). This kind of single chip coupled with IDE work decently well for applications such as AI robots, aerial photography, 3D printing, smartphone apps etc. Arduino’s special educational kits are very suitable for school level innovative STEM projects. STEM school programs have drawn international educators’ attention to the importance of the role played by their capability in enhancing students’ innovation potentials.
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| (Fig. 285) Arduino ATMega328P | (Fig. 286) Arduino Duemilanove |
Single chip microcontrollers accept only digital input signals, e.g. via USB ports. Handling chemical reaction analogue quantitative signal variables such as pH variation, solution conductance or colour intensity of aqueous solutions need additional sensors with A/D converter interface in addition to the Arduino chip board IDE.
Unlike purchasable data logger which schools adopted for immediate scientific experiments, available Arduno chip board IDEs need to be first programmed before use. While it is useful for STEM studies, it is not an appropriate science laboratory equipment for general use when the focus is on experiment only.